1. Field of the Invention
The present invention relates to a dressing apparatus for conditioning and regenerating a chemical mechanical polishing (referred to as CMP hereafter) pad; more specifically, the invention relates to a diamond disc dresser that cleans, flattens, and roughens the polishing pad.
2. Description of Related Art
A CMP device for polishing the surface of a semiconductor wafer includes a carrier for holding the semiconductor wafer and a polishing pad made of porous material polishes the wafer while retaining polishing slurry. The polishing slurry is a polishing fluid of certain grainy property. The carrier and pad are positioned such that the surface of the semiconductor wafer to be polished faces upward. The slurry is fed to the rear of the pad such that the porosity of the polishing pad allows the slurry to penetrate from the rear to the front of the pad.
Conventionally, two types of diamond disc dressers for conditioning the CMP pad are utilized by industry: annular disc type and spiky disc type.
An annular disc type dresser is a ring-shaped dressing apparatus with embedded synthetic diamond tool bits on its working surface. The main functions of the annular disc type dresser are to clean, roughen, and flatten the polishing pad of a CMP device. Nevertheless, it is extremely difficult to control the quality of the annular disc type dresser when it is being manufactured since the tiny diamond tool bits have to be permanently grafted to the working surface of the dresser with extreme evenness and tightness.
A spiky disc type dresser, on the other hand, is a disc dresser with a plurality of replaceable cylindrical spikes, wherein synthetic diamond bits are embedded on the tip portion of the cylindrical spikes. Since only a small area of the spiky type dresser is embedded with synthetic diamond bits, it is much simpler to manufacture the spiky disc type dresser compared with that of the annular disc type dresser. However, the spiky disc type dresser is less effective in cleaning, flattening, and roughening the pad.